Light emitting diode device

Abstract

Described are light emitting diode (LED) devices including a combination of electroluminescent and photo-luminescent active regions in the same wafer to provide LEDs with emission spectra that are adjustable after epitaxial growth. The LED device includes a multilayer anode contact comprising a reflecting metal and at least one transparent conducting oxide layer in between the metal and the p-type layer surface. The thickness of the transparent conducting oxide layer may vary for LEDs fabricated with different emission spectra.

What is claimed is: 
     
       1. A light emitting diode (LED) device comprising:
 a mesa array comprising a first mesa and a second mesa separated by a trench, the first mesa and the second mesa comprising a photoluminescent quantum well, an n-type layer on the photoluminescent quantum well, an electroluminescent quantum well on the n-type layer, and a p-type layer on the electroluminescent quantum well, the first mesa comprising a multilayer contact on the p-type layer and the second mesa comprising a p-type contact on the p-type layer, the trench having at least one side wall and extending to an n-type current spreading layer on a substrate. 
 
     
     
       2. The LED device of  claim 1 , further comprising a nucleation layer on the substrate and a defect reduction layer on the nucleation layer. 
     
     
       3. The LED device of  claim 1 , wherein the multilayer contact is a bilayer contact comprising a reflecting metal layer on a transparent conductive oxide layer. 
     
     
       4. The LED device of  claim 3 , wherein the reflecting metal layer comprises one or more of silver (Ag), nickel (Ni), aluminium (Al), and titanium (Ti). 
     
     
       5. The LED device of  claim 3  wherein the transparent conductive oxide layer comprises one or more of indium tin oxide (ITO), gallium oxide (Ga 2 O 3 ), zinc oxide (ZnO), tin oxide (SnO 2 ), and indium zinc oxide (InZnO). 
     
     
       6. The LED device of  claim 1 , wherein the electroluminescent quantum well emits a first light having a first wavelength and the photoluminescent quantum well absorbs at least a portion of the first light and emits a second light having a longer wavelength than the first light. 
     
     
       7. The LED device of  claim 6 , wherein the electroluminescent quantum well comprises multiple quantum wells emitting a same wavelength of light. 
     
     
       8. The LED device of  claim 6 , wherein the photoluminescent quantum well comprises multiple quantum wells emitting a same wavelength of light. 
     
     
       9. The LED device of  claim 1 , further comprising an n-type contact in the trench on the n-type current spreading layer. 
     
     
       10. The LED device of  claim 1 , wherein the substrate is a transparent substrate. 
     
     
       11. The LED device of  claim 10 , further comprising a dichroic reflector on the substrate opposite the n-type current spreading layer. 
     
     
       12. A light emitting diode (LED) device comprising:
 a mesa array comprising a first mesa and a second mesa separated by a trench, the first mesa and the second mesa comprising a photoluminescent quantum well, an n-type layer on the photoluminescent quantum well, an electroluminescent quantum well on the n-type layer, and a p-type layer on the electroluminescent quantum well, the first mesa comprising a first contact on the p-type layer, the first contact comprising a first reflecting metal layer on a first transparent conductive oxide layer, the first transparent conductive oxide layer having a first thickness, and the second mesa comprising a second contact on the p-type layer, the second contact comprising a second reflecting metal layer on a second transparent conductive oxide layer, the second transparent conductive oxide layer having a second thickness, and the trench having at least one side wall and extending to an n-type current spreading layer on a substrate. 
 
     
     
       13. The LED device of  claim 12 , further comprising a nucleation layer on the substrate and a defect reduction layer on the nucleation layer. 
     
     
       14. The LED device of  claim 12 , wherein the first reflecting metal layer and second reflecting metal layer independently comprises one or more of silver (Ag), nickel (Ni), aluminium (Al), and titanium (Ti). 
     
     
       15. The LED device of  claim 12 , wherein the first transparent conductive oxide layer and the second transparent conductive oxide layer independently comprise one or more of indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), and indium zinc oxide (InZnO). 
     
     
       16. The LED device of  claim 12 , wherein the difference between the first thickness and the second thickness is in a range of from 40 nm to 60 nm. 
     
     
       17. The LED device of  claim 12 , wherein the electroluminescent quantum well emits a first light having a first wavelength and the photoluminescent quantum well absorbs at least a portion of the first light and emits a second light having a longer wavelength than the first light. 
     
     
       18. The LED device of  claim 12 , further comprising an n-type contact in the trench on the n-type current spreading layer. 
     
     
       19. The LED device of  claim 18 , further comprising a dichroic reflector on the substrate opposite the n-type current spreading layer.